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Filtering Out HIV

Scientists looking to block HIV's evasions of the immune system found an unlikely source of inspiration: the spam filter.

By Rachael Moeller Gorman // Summer 2012
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Scientists looking to block HIV’s evasions of the immune system found an unlikely source of inspiration: the spam filter.

In the early days of e-mail, spammers went unchecked, sending scores of unwanted messages to unsuspecting in boxes. But in 1997, computer scientist David Heckerman and colleagues at Microsoft began creating ways to stop this flood of junk mail; the spam filter was born. Spammers soon realized their messages were being fended off, however, and altered e-mails to avoid detection. Heckerman just as quickly adapted his algorithm, forcing spammers to make still more changes, and so on. Because spam’s objective is to coax people to go to Websites and enter credit card numbers, Heckerman’s team compiled a continually updated list of spammers’ Websites and created an algorithm to scan e-mail for links to those sites and to remove junk messages before they reached in boxes. Heckerman says this tug-of-war is similar to what happens between a virus such as HIV and the human immune system. “Spammers mutate their message to work around the spam filters, and HIV mutates to avoid attack by our immune system,” he says.

Heckerman, who also is trained as a physician, went on to direct the eScience Research Group at Microsoft Research, where he developed probability models to examine how HIV evolved under certain evolutionary pressures. One model, PhyloD, helps find regions of the virus’s DNA that are mutating, most likely as a result of pressures from the immune system. PhyloD examines HIV one amino acid at a time, determining whether a patient’s immune system causes an amino acid to change at a given position, thus creating a hole for the “spam” to slip through the “filter.”

Some 30 scientific papers have resulted from Heckerman’s academic collaborations. Scientists may one day use such information to create a resistance-proof vaccine—the ultimate spam filter.

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